34G RECORD OJ'' SCIENCE FOR l,S87 AND 1888. 



Cross, Whitman On some erui)tive rocks iioui Caster Couuty, Colorado. Proc. 

 Colo. Sci. Soc, 1887, pp. 228-250. 



The rocks described are, (1) rhyolites, with primary corroded garnets; (2) 

 trachytes, apparently allied to the so-called sauidiuoligoclase trachytes of the 

 Siehengebirge in Germany; (.3) syenites; (4) peridotites, containing essential 

 hornblende and hypersthene, with accessory biotite, plagioclase, apatite, pyrrho- 

 tite, and sillimanito; (5) angite diorite, containi7ig olivine; (6) sanidin bearing 

 .indesite, in which the oligoclase crystals are nearly always snrrounded by a zone 

 of orthoclase. 



Dalmer, Karl. Die Quartztrachyte von Campiglia nnd deren Beziehnngen zn 

 granitporphyrartigen nnd granitischen Gesteinen. Neues Jahrb. Min., GeoL, 

 etc., 1887, II Band, p. 206. 



Derby, Orville A. Ou nepheliue rocks in Brazil, with special reference to the as- 

 sociation of phonolite and foyaite. Qnar. Jonr. Geol. Soc, No. 171, Augnst, 

 1887, vol. XLiii, p. 457. 



Describes the geological occnrrence and, to a certain extent, the lithological 

 characters of some peculiarly interesting nephelineandlencite rocks in the prov- 

 inces of Rio de Janeiro, Sao Paulo, and Miu.as-Geraes, Brazil. The more striking 

 features of the paper are the conclusions reached regarding the relations of the 

 phonolites and foyaites (eheolite syenite), the phonolite not only showing in- 

 clnsious of foyaite, but also the foyaite containing inclusions of phonolite, all 

 appearances indicating that they are both portions of the same magma ; that, in 

 short, the phonolite occurs as a perijiheral facies of the foyaite. A second re- 

 markable feature is the occurrence of leucite in rocks of undonbted paleozoic age. 

 The full significauce of these discoveries may be best comprehended by those 

 not specialists in this line of work if it be stated that the eheolite syenites are 

 deep seated or plntomc rocks of paleozoic age, and of which the phonolites have 

 been considered the effusive tertiary or post-tertiary equivalents. Moreover the 

 mineral leucite np to this time has been found as a constituent only of post-ter- 

 tiary lavas. The two discoveries, it will be observed, having a very important 

 bearing upon the subject of rock history and classificatiou, and bringing once 

 moi'e proof of the ntter impossibility of relying upon mineral composition or 

 structure as a guide to geological age. The conclusions reached by Dr. Derby 

 may be best nnderstood by quoting the author's exact words. He feels convinced 

 of, (1) the substantial identity as regards mode of occnrrence and geological age 

 of the CaldaS phonolites and foyaites ; (2) the connection of the latter through 

 the phonolites with a typical volcanic series containing both deep-seated and 

 aerial types of deposits ; (.3) the equal, if not greater, antiquity of the leucite 

 rocks as compared with the nepheline rocks, whether felsitic as phonolite, or 

 granitic as foyaite; and (4) the probable paleozoic age of the whole eruptive se- 

 ries. 



Diller, J. S., and George F. Kunz. Is there a diamond tiekl in Kentucky? Sci- 

 ence, September, 1887, vol. x, p. 140. 



Elsden, J.Vincent. Notes on the Igneous Rocks of the Lleyn Promontory. Geol. 

 Mag., July, 1888, p. :503. 



FoUQUE, M. Sur les nodules de la grauulite de Ghistorrai iirds Fonni (Sardaigne). 

 Bull. Soc. Franijaise Miu^ralogie, February, 1887, vol. x, p. 57. 



The nodules occur in a granulite consisting of quartz, orthoclase, oligoclase, 

 and both Avhite and black mica. They are rounded in outline and consist of an 

 irregular nucleus of the same composition and structure as the inclosing rock 

 surrounded by a shell composed of concentric layers of albite and biotite. 



Petrographie de PH(5ranlt. Les porphyrites de Gabian. Note de MM. P. 



De Ronville et Auguste Dilage, presented by M. Fouque. Comptes Rendus, 

 October 22, 1888, p. (m. 



Fox, Howard, and Alex. Somervail. On the occurrence of Porphyritic Structure 

 in some rocks of the Lizard district. Geol. Mag., February, 1888, p. 75. 



